I read this great blog post last year, on mapping an entire years worth of travel. I decided to do a little experiment this October, and track my routes to the many different schools that I worked at this month. Each day I traced my route in photoshop on different layers. I used the same sized line for my pen tool, but due to my messy tracing abilities, the routes I travelled more often tended to become thicker over time. Here is the result: